In coal pulverizers of the vertical spindle type, hardened grinding elements are used for the fine crushing of coal. The hardened grinding elements may vary in design, but all are intended to capture raw unground coal particles between two hardened surfaces. The grinding elements crush the raw coal particles in a bowl during normal mill operation.
In certain vertical spindle coal pulverizer designs, the grinding elements are each shaped similarly to a large diameter tire or wheel. This type of grinding element may be referred to as a roll wheel assembly. These roll wheel assemblies are common in certain types of vertical spindle coal pulverizers.
In other types of vertical spindle coal pulverizers, the grinding elements are more cylindrical in shape. These types of grinding elements are referred to as journal assemblies.
The roll wheel assemblies and the journal assemblies are located and positioned in the mill by large bracket assemblies containing pivot bearings, locating arms, and roll wheel/journal bearings. The function of these large bracket assemblies is to not only locate and position the roll wheel/journal assemblies, but to also provide a mechanism for imparting additional forces upon the roll wheel/journal assemblies and, thus, the raw coal particles in the bowl. This additional force increases the efficiency of grinding the raw coal particles and increases the grinding capacity of any vertical spindle type coal pulverizer.
The conventional means which is used in a vertical spindle coal pulverizer for imparting additional force upon the roll wheel/journal assemblies involves a complicated shaft and plunger design. The plunger is attached to a shaft, and the shaft and plunger move together axially in a canister. The shaft is located in the canister by small guide bearings. The plunger extends out of the end of the canister and imparts a force on the roll pivot bracket by making direct contact with it. The direction of the force is not axial. Consequently, there are high-maintenance requirements due to excessive bearing wear and broken shafts.
There has not heretofore been provided a coal pulverizer having the features and advantages provided by the present invention.